JP7549871B2 - Vapor phase growth apparatus and epitaxial wafer manufacturing method - Google Patents

Description

The present invention relates to a vapor phase growth apparatus for vapor-growth of a semiconductor single crystal thin film on the main surface of a single crystal substrate, and a method for manufacturing an epitaxial wafer using the apparatus.

Epitaxial wafers in which a semiconductor single crystal thin film is formed on a single crystal substrate, for example, silicon epitaxial wafers in which a silicon single crystal thin film (hereinafter simply referred to as "thin film") is formed on the surface of a silicon single crystal substrate (hereinafter simply referred to as "substrate") by vapor phase growth, are widely used in electronic devices such as bipolar ICs and MOS-ICs. In recent years, in the manufacture of epitaxial wafers with a diameter of, for example, 200 mm or more, single-wafer vapor phase growth equipment is becoming mainstream, replacing the batch processing method of multiple wafers. In this system, a single substrate is rotated horizontally in a reaction vessel, and a thin film is vapor-grown while a source gas is supplied from one end of the reaction vessel to the other end in a substantially horizontal and unidirectional manner. In general, infrared radiation heating, high-frequency induction heating, resistance heating, or other methods are used to heat the substrate in the manufacture of silicon epitaxial wafers, and the temperature of the silicon substrate and susceptor rises, but the temperature of the wall of the reaction vessel is kept low, creating a so-called cold wall environment.

In single-wafer vapor phase growth apparatus, the source gas is usually supplied from a gas inlet formed at one end of a reaction vessel via a gas supply pipe, and after the source gas flows along the main surface of the substrate, it is discharged from an outlet on the other end of the vessel. When manufacturing epitaxial wafers using an apparatus with such a structure, it is known that increasing the flow rate of the source gas along the main surface of the substrate is effective in increasing the growth rate of the silicon single crystal thin film. For example, Non-Patent Document 1 discloses that when manufacturing silicon epitaxial wafers, the growth rate of the silicon single crystal layer deposited on the substrate can be increased by increasing the relative speed between the main surface of the substrate and the source gas by increasing the susceptor rotation speed.

In the experiment disclosed in Non-Patent Document 1, the concentration and flow rate of the source gas supplied to the reaction vessel are set constant, and it is shown that when the susceptor rotation speed is increased under these conditions, the growth rate of the silicon single crystal layer increases. In addition, Non-Patent Document 2 thermodynamically shows that in the above-mentioned cold wall environment, when the gas phase temperature increases during growth of the silicon single crystal layer, the growth rate of the single crystal layer decreases in the region where the transport rate of the source gas components is rate-limiting (i.e., the diffusion layer on the main surface of the substrate).

In other words, if the gas flow rate at the main surface of the substrate increases, the heat transfer from the main surface of the substrate is promoted, lowering the temperature of the main surface of the substrate, and the increased gas flow rate reduces the thickness of the diffusion layer at the main surface of the substrate, increasing the concentration gradient of the source gas components in the diffusion layer. These factors are thought to increase the efficiency of the chemical reaction that produces silicon single crystals from the source gas, and thus increase the growth rate of the silicon single crystal layer.

Patent No. 6068255 JP 2005-183510 A JP 2011-165948 A

"Numerical calculation of 450 mm diameter silicon epitaxial growth rate": Abstracts of the 75th Autumn Meeting of the Japan Society of Applied Physics (Autumn 2014, Hokkaido University) 19a-A19-1 "Simulation of the Si epitaxial thin film fabrication process": Journal of the Vacuum Society of Japan, Vol. 49 (2006), pp. 525-529

From the above considerations, it is believed that in order to increase the flow rate of the source gas on the main surface of the substrate in a single-wafer vapor phase growth apparatus and increase the growth rate of the semiconductor single crystal layer, it is effective to adopt a structure that reduces the spatial height between the main surface of the substrate, which serves as the source gas flow path, and the underside of the ceiling plate of the reaction vessel. Specifically, in the semiconductor single crystal growth process, the above spatial height can be reduced by adopting a structure in which the position of the susceptor that holds the substrate is closer in the height direction to the underside of the top plate of the reaction vessel.

On the other hand, as the growth rate of the semiconductor single crystal layer increases, the in-plane film thickness distribution width of the semiconductor single crystal layer that is formed tends to increase. For example, when the requirements for flatness of the main surface of the epitaxial wafer on which elements are fabricated become particularly strict due to the miniaturization of electronic devices, it may be advantageous to keep the growth rate of the semiconductor single crystal layer low. In this case, it is considered effective to adopt a structure in which the position of the susceptor is separated from the underside of the ceiling plate of the reaction vessel, that is, a structure in which the height of the space between the main surface of the substrate, which serves as the flow path of the raw material gas, and the underside of the ceiling plate of the reaction vessel is increased, thereby reducing the flow rate of the raw material gas.

For example, Patent Document 1 discloses a vapor phase growth apparatus incorporating a mechanism for raising and lowering a susceptor (and susceptor cover) within a reaction vessel. However, the purpose of raising and lowering the susceptor in Patent Document 1 is to improve the ease of operation during maintenance of the apparatus, and there is no mention at all of the technical idea of adjusting the flow rate of the source gas by changing the susceptor position during the growth of a semiconductor single crystal layer. Even if a mechanism similar to that in Patent Document 1 were adopted to adjust the flow rate of the source gas, the following problems would arise.

In other words, it is known that the thickness distribution of the semiconductor single crystal layer formed on the substrate in a single-wafer vapor phase growth apparatus is significantly affected by the temperature distribution within the main surface of the substrate, and the thickness of the semiconductor single crystal layer is particularly likely to vary toward the larger side at the outer periphery of the substrate, where temperature drops are more likely to occur. To prevent this, a preheat ring is generally provided around the susceptor in single-wafer vapor phase growth apparatus to ensure uniform heating of the outer periphery of the substrate.

However, the apparatus of Patent Document 1 does not include the preheat ring. Even if it were included, if the height position of the preheat ring is fixed within the reaction vessel, the relative positional relationship in the height direction between the substrate on the susceptor and the preheat ring will vary significantly as the height position of the susceptor is changed. As a result, if the height misalignment between the preheat ring and the substrate increases due to a change in the susceptor holding position, the preheat ring will not be able to uniformly heat the outer periphery of the substrate, leading to greater variation in the film thickness of the semiconductor single crystal layer. In addition, a large step is created between the main surface of the substrate and the preheat ring, which makes it easy for the flow of the source gas to become turbulent as it passes through this step, and this can also be a factor in film thickness variation of the semiconductor single crystal layer.

The objective of the present invention is to enable the flow rate of the source gas to be adjusted by changing the susceptor position in a vapor phase growth apparatus equipped with a preheat ring around the susceptor, and to reduce the effect of changing the susceptor position on the film thickness variation of the semiconductor single crystal layer.

The vapor phase growth apparatus of the present invention is for vapor-growing a semiconductor single crystal thin film on a main surface of a single crystal substrate, and has a reaction vessel body having a gas inlet formed at a first end side in the horizontal direction and a gas outlet formed at a second end side, and is configured so that a raw material gas for forming the semiconductor single crystal thin film is introduced into the reaction vessel body from the gas inlet, flows in a direction along the main surface of the single crystal substrate which is held and rotated approximately horizontally in the internal space of the reaction vessel body, and is then discharged from the gas outlet, and a preheat ring is arranged to surround the susceptor. In order to solve the above problems, the device is further characterized by including a susceptor position change mechanism that changes the height direction holding position of the susceptor in the reaction vessel body based on the elevation of the susceptor in order to change in a stepped or stepless manner the height direction dimension of the raw material gas flow space formed between the main surface of the single crystal substrate mounted on the susceptor and the underside of the upper wall of the reaction vessel body, and a preheat ring position change mechanism that changes the height direction holding position of the preheat ring in the reaction vessel body based on the elevation of the preheat ring in a manner that follows the change in the height direction holding position of the susceptor.

In addition, the epitaxial wafer manufacturing method of the present invention has a reaction vessel body having a gas inlet formed at a first end side in a horizontal direction and a gas outlet formed at a second end side, and a single crystal substrate is rotated and supported approximately horizontally on a disk-shaped susceptor that is rotated in the internal space of the reaction vessel body, and a raw material gas for forming a semiconductor single crystal thin film introduced into the reaction vessel body from the gas inlet flows along the main surface of the single crystal substrate and is then discharged from the gas outlet, and a preheat ring is disposed to surround the susceptor, and a preheat ring is disposed between the main surface of the single crystal substrate mounted on the susceptor and the lower surface of the upper wall of the reaction vessel body. In order to change the height dimension of the raw material gas flow space formed between the susceptor and the preheat ring, a susceptor position change mechanism changes the height direction holding position of the susceptor in the reaction vessel body based on the elevation of the susceptor, and a preheat ring position change mechanism changes the height direction holding position of the preheat ring in the reaction vessel body based on the elevation of the preheat ring in a manner that follows the change in the height direction holding position of the susceptor. A single crystal substrate is placed in the reaction vessel body of a vapor phase growth apparatus equipped with the susceptor position change mechanism, and a raw material gas is circulated in the reaction vessel body to cause vapor phase epitaxial growth of a semiconductor single crystal thin film on the single crystal substrate, thereby obtaining an epitaxial wafer.

In the vapor phase growth apparatus of the present invention, it is desirable that the preheat ring position changing mechanism is configured to change the height-wise holding position of the preheat ring so that the main surface of the single crystal substrate on the susceptor coincides with the upper surface of the preheat ring as the height-wise holding position of the susceptor is changed.

The susceptor position changing mechanism can be configured to change the height direction holding position of the susceptor between a susceptor-side first position, where the height direction dimension of the raw material gas flow space is a first dimension, and a susceptor-side second position, where the height direction dimension of the raw material gas flow space is a second dimension smaller than the first dimension. In this case, the preheat ring position changing mechanism can be configured to change the height direction holding position of the preheat ring between a ring-side first position and a ring-side second position, which correspond to the susceptor-side first position and the susceptor-side second position, respectively.

The susceptor is rotated, for example, via a rotating shaft member whose upper end is connected to the lower surface of the susceptor. In this case, the susceptor position changing mechanism is configured to raise and lower the susceptor together with the rotating shaft member. The preheat ring position changing mechanism can be configured to include a lifting sleeve that is arranged coaxially on the outside of the rotating shaft member and can be raised and lowered along the axis of the rotating shaft member while allowing the rotating shaft member to be rotated, a connecting member that connects the lifting sleeve and the preheat ring, and a lifting drive unit that drives the lifting sleeve and connecting member to be raised and lowered together.

In addition, in the vapor phase growth apparatus of the present invention, lift pins that lift up the semiconductor substrate on the susceptor by pushing it up from below can be provided with their lower ends protruding downward from the susceptor. In this case, a configuration can be adopted in which the base end of a lift pin drive arm for urging the lift pin upward from below is connected to the lift sleeve.

In the vapor phase growth apparatus of the present invention, a lower liner formed in an annular shape and positioned so that its outer peripheral surface faces the gas inlet can be provided around the susceptor in the reaction vessel body, and an upper liner can be provided facing the lower liner above the lower liner to guide the flow of raw material gas that is supplied from the gas inlet and that hits the outer peripheral surface of the lower liner and disperses in the circumferential direction while passing over the lower liner, onto the main surface of the single crystal substrate on the susceptor. The lower liner can also be configured to include a liner base that forms the outer peripheral surface and is fixed in its vertical position relative to the reaction vessel body, and a liner movable part that has a preheat ring attached to its upper surface and is slidable in the vertical direction together with the preheat ring relative to the liner base. In this case, the liner movable part and a coupling auxiliary part that has one end coupled to the lift sleeve and the other end coupled to the liner movable part constitute the aforementioned coupling member.

In this configuration, the preheat ring can be attached to the movable liner part so that its upper surface coincides with the upper surface of the movable liner part. The movable liner part has a cylindrical sliding part that opens to the upper surface of the liner base and has its base end inserted into a groove that is engraved along the circumferential direction of the liner base, and slides up and down within the groove, and a flange part that extends radially inward from the upper edge of the sliding part, and the preheat ring can be attached to the upper surface of the flange part.

The vapor phase growth apparatus of the present invention is configured so that the height direction holding position of the susceptor within the reaction vessel body can be changed by raising and lowering the susceptor using a susceptor position changing mechanism. By changing the susceptor position, the height direction dimension of the source gas flow space formed between the main surface of the single crystal substrate mounted on the susceptor and the underside of the upper wall of the reaction vessel body can be changed in a stepwise or stepless manner, making it possible to adjust the flow rate of the source gas when growing a semiconductor single crystal layer on the single crystal substrate, and therefore the semiconductor single crystal layer.

In the present invention, a preheat ring position change mechanism is provided that changes the height-wise holding position of the preheat ring in the reaction vessel body based on the elevation of the preheat ring in response to changes in the height-wise holding position of the susceptor. This makes it possible to reduce the positional deviation in the height direction between the preheat ring and the substrate even when the susceptor holding position is changed, effectively reducing the effects of insufficient uniform heating of the outer periphery of the substrate by the preheat ring and turbulence in the flow of raw material gas due to the step between the main surface of the substrate and the preheat ring, and thus reducing the effects on the film thickness variation of the resulting semiconductor single crystal layer.

FIG. 1 is a side cross-sectional view showing an example of a vapor phase growth apparatus of the present invention. Schematic diagram of a silicon epitaxial wafer. FIG. 2 is a side cross-sectional view showing an example of an ascending and descending sliding portion of a preheating ring in the vapor phase growth apparatus of FIG. 1 . FIG. 2 is a perspective view showing a lift pin drive mechanism of the vapor phase growth apparatus of FIG. 1 . FIG. 13 is a plan view showing an example of an arrangement of a joining auxiliary part that raises and lowers a preheating ring. FIG. 2 is an explanatory diagram of the operation of the vapor phase growth apparatus of FIG. 1 . FIG. 2 is a schematic plan view of the vapor phase growth apparatus of FIG. 1 . FIG. 2 is a block diagram of a control system for the vapor phase growth apparatus of FIG. 1 . FIG. 9 is a flowchart showing an example of a process flow of a control program in the control system of FIG. 8 . FIG. 4 is a schematic diagram showing an example of a screw shaft mechanism. FIG. 13 is a side cross-sectional view showing a modified example of the ascending and descending sliding portion of the preheating ring.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a side cross-sectional view showing a schematic example of a vapor phase growth apparatus 1 according to the present invention. As shown in FIG. 2, the vapor phase growth apparatus 1 is for vapor-growing a silicon single crystal thin film EL on a main surface (upper surface) PP of a silicon single crystal substrate W to manufacture a silicon epitaxial wafer EW. As shown in FIG. 1, the vapor phase growth apparatus 1 has a reaction vessel body 2 having a gas inlet 21 formed at a first end side in the horizontal direction and a gas outlet 22 formed at a second end side. A source gas G for forming a thin film is introduced into the reaction vessel body 2 from the gas inlet 21, flows along the main surface of a silicon single crystal substrate W (hereinafter, also simply referred to as "substrate W") that is rotated and held substantially horizontally in the internal space 5 of the reaction vessel body 2, and is then discharged from the gas outlet 22. The reaction vessel body 2 is entirely formed of a metal material such as quartz or stainless steel together with other internal components, and has a structure divided into a lower body part 3 and an upper body part 4. The internal space 5 is composed of a source gas flow space 5A defined by the upper body 4 of the main body and an equipment arrangement space 5B defined by the lower body 3 of the main body.

Figure 7 is a plan view showing a schematic configuration of the vapor phase growth apparatus 1. The gas inlet 21 in Figure 1 is composed of multiple gas inlets 21A and 21B arranged in a horizontal direction. The raw material gas G is introduced from the gas inlets 21A and 21B to the internal space 5 through the gas pipe 50. In this embodiment, the gas pipe 50 branches into an inner pipe 53 and an outer pipe 51, and the flow rate of each raw material gas can be adjusted by gas flow regulators 52 and 54. The inner pipe 53 has an inner gas inlet 21A opening. The outer pipe 51 further branches into branch pipes 55 and 55, each of which has an outer gas inlet 21B opening. The raw material gas G1 from the gas inlet 21A is supplied to the region forming the center of the substrate W, and the raw material gas G2 from the gas inlet 21B is supplied to the regions at both the left and right ends, respectively, and then collected at the gas exhaust port 22 and exhausted to the gas exhaust pipe 60.

The source gas G (G1, G2) is for vapor-phase growth of a silicon single crystal thin film on the substrate W, and is selected from silicon compounds such as SiHCl ₃ , SiCl ₄ , SiH ₂ Cl ₂ , SiH ₄ , and Si ₂ H _6. The source gas G is appropriately mixed with B ₂ H ₆ or PH ₃ as a dopant gas, and H ₂ , N ₂ , Ar, and the like as a dilution gas. In addition, when performing substrate pretreatment (for example, removal of a natural oxide film or attached organic matter) prior to vapor-phase growth of a thin film, a pretreatment gas in which a corrosive gas appropriately selected from HCl, HF, ClF ₃ , NF ₃ , and the like is diluted with a dilution gas is supplied into the reaction vessel body 2, or a high-temperature heat treatment is performed in an H ₂ atmosphere.

In FIG. 1, a disk-shaped susceptor 9 rotated by a motor 40 around a vertical axis of rotation O is disposed in the internal space 5 of the reaction vessel body 2, and only one substrate W for manufacturing the silicon epitaxial wafer EW of FIG. 2 is disposed in a shallow counterbore 9B (see FIG. 4) formed on the upper surface of the susceptor. That is, the vapor phase growth apparatus 1 is configured as a horizontal single-wafer vapor phase growth apparatus. The substrate W has a diameter of, for example, 100 mm or more. Also, as shown in FIG. 1, infrared heating lamps 11 for heating the substrate are disposed at a predetermined interval above and below the reaction vessel body 2 corresponding to the placement area of the substrate W. Also, a preheating ring 32 is disposed in the reaction vessel body 2 so as to surround the susceptor 9. The aforementioned raw material gas flow space 5A is formed between the main surface of the substrate W mounted on the susceptor 9 and the lower surface of the ceiling plate 4C of the reaction vessel body 2.

The susceptor 9 is rotated by a motor 40 via a rotating shaft member 15, the upper end of which is connected to the underside of the susceptor 9. The base ends of multiple susceptor support arms 15D are connected to the tip of the rotating shaft member 15. Each susceptor support arm 15D extends in the radial direction of the susceptor 9 with its tip side inclined upward, and each tip is connected to the outer peripheral region of the underside of the susceptor 9 by a connecting pin 15c.

The vapor phase growth apparatus 1 is provided with a susceptor position changing mechanism 39 for changing the height dimension of the source gas flow space 5A. The susceptor position changing mechanism 39 is for changing the height holding position of the susceptor 9 in the reaction vessel body 2 based on the elevation of the susceptor 9. The susceptor position changing mechanism 39 is configured to raise and lower the susceptor 9 together with the rotating shaft member 15 (and the motor 40), and in this embodiment, the elevation drive unit is configured with an air cylinder 41 (which may be an electric cylinder). The tip of the cylinder rod of the air cylinder 41 is connected to a susceptor assembly including the rotating shaft member 15 and the motor 40 via the substrate BP1.

The height direction holding position of the susceptor 9 in the silicon single crystal thin film growth process is selectively set to either the susceptor side first position (corresponding to the rod retracted position P1 of the air cylinder 41 in FIG. 6; hereinafter also referred to as the susceptor side first position P1) where the height direction dimension d of the raw material gas flow space 5A is the first dimension h shown in FIG. 1, or the susceptor side second position (corresponding to the rod advanced position P2 of the air cylinder 41; hereinafter also referred to as the susceptor side second position P2) where the height direction dimension d is the second dimension h' (smaller than the first dimension h) shown in FIG. 6. In this configuration, the values that can be set for the height direction dimension of the raw material gas flow space 5A are limited to two types, the first dimension h and the second dimension h', but the configuration of the lifting and lowering drive unit can be significantly simplified.

Next, the vapor phase growth apparatus 1 in FIG. 1 is provided with a preheat ring position change mechanism 12. The preheat ring position change mechanism 12 is for changing the height direction holding position of the preheat ring 32 in the reaction vessel body 2 based on the lifting and lowering of the preheat ring 32 in a manner that follows the change in the height direction holding position of the susceptor 9. In this embodiment, the preheat ring position change mechanism 12 includes a lift sleeve 12B that is arranged coaxially on the outside of the rotating shaft member 15 and along the axis of the rotating shaft member 15 so as to be liftable and lowerable relative to the rotating shaft member 15 while allowing the rotating shaft member 15 and thus the susceptor 9 to be rotated, a coupling member (liner movable part 33 and coupling auxiliary part 35: described later) that couples the lift sleeve 12B and the preheat ring 32, and a lift drive part (air cylinder 42) that drives the lift sleeve 12B and the coupling member to lift and lower together. With this configuration, the base for driving the preheat ring 32 to rise and fall can be concentrated around the rotating shaft member 15 in the form of a lift sleeve 12B, which in turn makes it possible to configure the preheat ring position change mechanism 12 compactly within the limited space (equipment arrangement space 5B) below the susceptor 9 inside the reaction vessel body 2.

As shown in FIG. 1, an annular lower liner 29 is provided around the susceptor 9 in the reaction vessel body 2, with its outer circumferential surface facing the gas inlet 21. An annular upper liner 30 is provided above and facing the lower liner 29. The source gas G supplied from the gas inlet 21 hits the outer circumferential surface of the lower liner 29 and disperses in the circumferential direction, attempting to flow over the lower liner 29. The upper liner 30 serves to guide the flow of the source gas G onto the main surface of the silicon single crystal substrate W on the susceptor 9.

The lower liner 29 includes a liner base 31 and a liner movable part 33. The liner base 31 is attached to the reaction vessel body 2 so that its vertical position is fixed. The liner movable part 33 has a preheating ring 32 attached to its upper surface, and is attached to the liner base 31 so that it can slide vertically together with the preheating ring 32. The liner base 31 forms the aforementioned outer peripheral surface that receives the flow of the raw material gas G supplied from the gas inlet 21. The aforementioned coupling member is composed of the liner movable part 33 and a coupling auxiliary part 35, one end of which is coupled to the lift sleeve 12B and the other end of which is coupled to the liner movable part 33. In FIG. 1, the coupling auxiliary part 35 is formed in an arm shape with a base end side coupled to the lift sleeve 12B and a tip end side coupled to the liner movable part 33. For example, as shown in FIG. 5, a plurality of coupling auxiliary parts 35 (four in the configuration of FIG. 5) are provided around the central axis of the lift sleeve 12B. In FIG. 5, the susceptor 9 and preheat ring 32 are omitted.

As shown enlarged in FIG. 3, the liner movable part 33 includes a cylindrical sliding part 33A and a flange part 33B extending radially inward from the upper end edge of the sliding part 33A. Meanwhile, a groove part 31g is engraved in the liner base 31, which opens on the upper surface of the liner base 31 and runs along the circumferential direction. The sliding part 33A of the liner movable part 33 is inserted at its lower end into the groove part 31g, and slides up and down within the groove part 31g. The preheat ring 32 is attached to the upper surface of the flange part 33B. In the above structure, the sliding part 33A of the liner movable part 33, to which the preheat ring 32 is directly attached, slides in the height direction inside the groove part 31g while fitting into the groove part 31g of the liner base 31, making it easier to maintain the horizontality of the preheat ring 32 when changing the height-direction holding position of the preheat ring 32.

As shown in FIG. 1, in this embodiment, the preheat ring position change mechanism 12 has its lifting drive unit configured by an air cylinder 42. The tip of the cylinder rod of the air cylinder 42 is connected to the liner movable part 33 via the substrate BP2. The preheat ring position change mechanism 12 changes the height direction position of the preheat ring 32 between a ring side first position (see FIG. 6: rod retraction position P1' of the air cylinder 42: hereinafter also referred to as the ring side first position P1') corresponding to the susceptor side first position (see FIG. 6: symbol P1) shown in FIG. 1, and a ring side second position (corresponding to FIG. 6: rod forward position P2': hereinafter also referred to as the ring side second position P2') corresponding to the susceptor side second position (see FIG. 6: symbol P2) shown in FIG. 6. This also greatly simplifies the configuration of the lifting drive unit of the preheat ring position change mechanism 12.

In this embodiment, as shown in Figures 1 and 3, the preheat ring position change mechanism 12 is configured to change the heightwise holding position of the preheat ring 32 so that the main surface of the silicon single crystal substrate W on the susceptor 9 coincides with the upper surface of the preheat ring 32 as the heightwise holding position of the susceptor 9 is changed. Even when the heightwise holding position of the preheat ring 32 is changed, by aligning the upper surface of the preheat ring 32 with the main surface of the silicon single crystal substrate W on the susceptor 9, no step is generated between the main surface of the substrate and the preheat ring 32, and disturbance of the raw material gas flow when passing through it can be effectively suppressed.

As shown in FIG. 3, the preheat ring 32 is attached to the liner movable part 33 so that its upper surface coincides with the upper surface of the liner movable part 33. This eliminates any step between the upper surfaces of the preheat ring 32 and the liner movable part 33 (lower liner), and more effectively suppresses turbulence in the raw gas flow. In this embodiment, the preheat ring 32 is attached to the liner movable part 33 by being fitted into a countersunk portion 33K formed along the inner peripheral edge of the upper surface of the flange portion 33B.

1, the susceptor 9 is provided with lift pins 13, which lift up the substrate W on the susceptor 9 by pushing it up from below, with their lower ends protruding downward from the susceptor 9. FIG. 4 is a perspective view showing the lift pin drive mechanism (parts related to the raising and lowering of the preheat ring 32, such as the coupling auxiliary part 35, are omitted). A plurality of lift pin insertion holes 14 are formed in the circumferential direction on the outer periphery of the bottom of the countersink 9B of the susceptor 9, penetrating the bottom from top to bottom. The upper end of the lift pin 13 is a head with a larger diameter than the base end, and the upper end of the insertion hole 14 is a countersink portion whose diameter is enlarged to match the head of the lift pin 13. The lower surface of the head of the lift pin 13 hits the bottom surface of the countersink portion of the insertion hole 14, preventing the lift pin from falling off the susceptor 9.

The base ends of the multiple lift pin drive arms 12A that urge the lift pins 13 upward from below are connected to the aforementioned lift sleeve 12B. With this configuration, the lift sleeve 12B is shared between the preheat ring position change mechanism 12 and the urging mechanism for the lift pins 13, reducing the number of parts.

Each lift pin drive arm 12A extends in the radial direction of the susceptor 9 with its tip inclined upward (in the illustrated example, three lift pin drive arms 12A are arranged at equal angular intervals around the central axis of the susceptor 9). In addition, each tip of the lift pin drive arm 12A is wider than the base end portion, and a lift plate 12C is formed that faces the lower end surface of the lift pin 13 from below.

When the lift sleeve 12B approaches the lower surface of the susceptor 9 along the rotating shaft member 15, the lift pins 13 are urged upward by the lift plate 12C of the lift pin drive arm 12A. As a result, the substrate W on the susceptor 9 is pushed up from below by the lift pins 13 and lifted up, making it easy to collect the substrate W after the silicon single crystal thin film has been formed. Note that it is also possible to lower the susceptor 9 and urge the lift pins 13 by retracting the susceptor 9 and rotating shaft member 15 (and the motor 40 and air cylinder 41) together using another air cylinder (not shown) or the like while fixing the height position of the lift sleeve 12B.

The operation of the vapor phase growth apparatus 1 will now be described.
As shown in Fig. 1, a substrate W is set on a susceptor 9, and after performing pretreatment such as removal of a natural oxide film if necessary, an air cylinder 41 of a susceptor position changing mechanism 39 is driven to set the height direction position of the susceptor 9 (and the substrate W supported thereby) to either a susceptor-side first position P1 shown in Fig. 1 or a susceptor-side second position P2 shown in Fig. 6. Accordingly, the height direction dimension of the source gas flow space 5A becomes a first dimension h where the flow rate of the source gas is small when set to the susceptor-side first position P1 (Fig. 1), and becomes a second dimension h'(<h) where the flow rate of the source gas is large when set to the susceptor-side second position P2 (Fig. 6).

Furthermore, by driving the air cylinder 42 of the preheat ring position changing mechanism 12, the height position of the preheat ring 32 is set to the corresponding ring side first position P1' when the susceptor side first position P1 (Figure 1) is set, and to the corresponding ring side second position P2' when the susceptor side second position P2 (Figure 6) is set. In either case, the upper surface position of the preheat ring 32 is aligned so as to be approximately flush with the main surface (upper surface) of the substrate W on the susceptor 9.

In this state, the substrate W is heated to a predetermined reaction temperature by the infrared heating lamps 11 while being rotated, and raw material gas G is introduced into the reaction vessel body 2 from the gas inlet 21. The raw material gas G flows toward the outer peripheral surface of the liner base 31 of the lower liner 29. The gas flow that hits the outer peripheral surface of the liner base 31 rides up onto the upper surface of the liner movable part 33, passes through the upper surface of the preheat ring 32, flows along the main surface of the substrate W, and is discharged from the gas exhaust port 22. During this process, as shown in FIG. 2, a silicon single crystal thin film EL is epitaxially grown on the main surface PP of the substrate W.

Here, in a single-wafer type vapor phase growth apparatus such as the vapor phase growth apparatus 1, the setting position shown in FIG. 1 is convenient when it is desired to keep the growth rate of the semiconductor single crystal layer low, for example, when the requirements for the flatness of the main surface of the epitaxial wafer on which the element is to be fabricated are particularly strict. On the other hand, the setting position of the susceptor 9 and the preheat ring 32 shown in FIG. 6 is convenient for increasing the growth rate of the semiconductor single crystal layer and improving production efficiency. In addition, with this setting position, the susceptor 9 is closer to the infrared heating lamps 11, so the heating rate when heating the substrate W to the target temperature is increased, and the heating sequence can be shortened. In addition, the increase in the gas filling rate of the raw material gas flow space 5A also contributes to the improvement of the heating rate of the substrate W.

And, as already explained, under all conditions, the position of the upper surface of the preheat ring 32 is aligned with the main surface (upper surface) of the substrate W on the susceptor 9, so that the insufficient uniform heating effect of the preheat ring 32 on the outer periphery of the substrate W and the influence of turbulence in the flow of the raw material gas resulting from the step between the main surface of the substrate W and the preheat ring 32 can be effectively reduced, and thus the influence on the variation in the film thickness of the obtained silicon single crystal layer can be reduced.

In addition, the vapor phase growth apparatus 1 is configured as a cold-wall type vapor phase growth apparatus. When such a cold-wall type vapor phase growth apparatus is adopted, Patent Document 3 suggests the possibility that the accumulation of silicon deposits, which are reaction products, on the inner wall of the quartz glass forming the reaction vessel body 2 during epitaxial growth can be suppressed by increasing the flow rate of the raw material gas. Based on the configuration of the present invention, for example, as shown in FIG. 6, by reducing the height dimension of the raw material gas flow space 5A and increasing the flow rate of the raw material gas, the accumulation of silicon deposits on the inner surface of the reaction vessel body ₂ can also be effectively suppressed. The above effect is considered to be particularly remarkable when conditions that are likely to cause the accumulation of silicon deposits are adopted, such as when epitaxial growth is performed at high temperature (e.g., 1150° C.) and reduced pressure (e.g., 60 Torr) using SiH 2 Cl ₂ (dichlorosilane S) as the silicon source gas.

An example of the control form of the vapor phase growth apparatus 1 will be described below. FIG. 8 is a block diagram showing the electrical configuration of the control system of the vapor phase growth apparatus 1. The control system is configured with a control computer 70 as the main controller. The control computer 70 has a structure in which a CPU 71, a ROM 72 (program storage unit) storing a control program 72a, a RAM 73 that serves as a work memory when the CPU 71 executes the control program 72a, an input/output unit 74 that electrically inputs and outputs control information, and the like are interconnected by an internal bus 75 (data bus + address bus).

The driving elements of the vapor phase growth apparatus 1 shown in FIG. 1 are connected to the control computer 70 as follows. The infrared heating lamps 11 are connected to the input/output unit 74 via the lamp control circuit 11c. A temperature sensor 15B for detecting the substrate temperature is also connected to the input/output unit 74. The gas flow regulators 52 and 54 each have a flow detection unit and a built-in valve (not shown), and by being connected to the input/output unit 74, they receive instructions from the control computer 70 and continuously control the source gas in each pipe using the built-in valve.

The motor 40 that drives the susceptor 9 is connected to the input/output unit 74 via a servo control unit 40c. The servo control unit 40c monitors the rotation speed of the motor 40 based on the pulse input from a pulse generator 40p (rotation sensor) attached to the output shaft of the motor 40, and controls the drive so that the rotation speed of the motor 40 (and thus the susceptor 9) is kept constant by referring to the rotation speed instruction value from the control computer 70. In addition, the air cylinder 41 that drives the susceptor 9 to move up and down is connected to the input/output unit 74 via a cylinder driver 41c, and the air cylinder 42 that drives the preheat ring 32 to move up and down is connected to the input/output unit 74 via a cylinder driver 41c (note that in a configuration in which the air cylinders 41 and 42 are incorporated, the screw shaft drive units 81 and 82 shown by dashed lines and described below are not necessary).

In this embodiment, the output of the infrared heating lamps 11 (i.e., the temperature of the substrate W during film formation), the flow rate of the outer source gas G2 controlled by the gas flow regulator 52, and the flow rate of the inner source gas G1 controlled by the gas flow regulator 54 are each changed appropriately according to the set values of the height direction position P of the susceptor and the height direction position P' of the preheat ring (i.e., the height direction dimension of the source gas flow space 5A).

In FIG. 1, when the height of the raw material gas flow space 5A changes, the radial distribution of the gas flow resistance on the main surface of the substrate W may change. In FIG. 7, when the flow rate of the inner raw material gas G1 and the flow rate of the outer raw material gas G2 are constant, the flow rate distribution and temperature distribution of the raw material gas distributed to the outer peripheral region of the main surface of the substrate W, as well as the flow rate distribution (or temperature distribution) of the raw material gas distributed to the inner peripheral region, may also change, and the film thickness distribution on the inner and outer periphery of the silicon single crystal thin film formed may change depending on the height value of the raw material gas flow space 5A set. As described above, changing and setting the flow rate of the inner raw material gas G1 and the flow rate of the outer raw material gas G2 (and also the temperature of the substrate W during film formation) depending on the height setting value of the raw material gas flow space 5A may be advantageous in eliminating such problems.

In this embodiment, as shown in Fig. 8, a set value table 72b referenced by the control program 72a is stored in the ROM 72 of the control computer 70. As shown in Fig. 9, this set value table 72b includes the values of the height direction holding position of the preheat ring (the ring side first position P1' and the ring side second position P2'), the temperature T1, T2, the flow rate F11, F12 (inside) and F21, F22 (outside) that correspond to multiple (here, two) height direction holding positions (the susceptor side first position P1 and the susceptor side second position P2) that can be set for the susceptor 9, respectively, and the corresponding values are read out as appropriate according to the set susceptor height value, and are stored in the corresponding memory in the RAM 73 and used for control. However, if there is little concern about the occurrence of such a defect, it is of course possible to set some or all of the flow rate of the inner source gas G1, the flow rate of the outer source gas G2, and even the temperature of the substrate W during film formation to certain appropriate values, regardless of the height value of the source gas flow space 5A.

An example of the flow of the operation of the vapor phase growth apparatus 1 by the control program 72a will be described with reference to FIG. 10. In S101, the height direction position P of the susceptor is set, and in S102, the corresponding height direction position P' of the preheat ring is set. In S103, the susceptor 9 and the preheat ring 32 are moved to the work receiving position. The work receiving position can be set as the susceptor height (susceptor side first position P1: see FIG. 6) when the height of the raw material gas flow space 5A is large, for example, as shown in FIG. 1. In S104, the work (substrate W) is transferred from the preparation chamber (not shown) of the vapor phase growth apparatus 1 and set on the susceptor 9. In S105, the infrared heating lamp 11 is operated to heat the inside of the internal space 5 to the set temperature. In S106, the air cylinders 41 and 42 are operated to move the susceptor and the preheat ring to the set height direction holding position. Then, the process proceeds to S107, where the rotation of the susceptor 9 is started, and in S108, the flow of the raw material gas is started at the set flow rate. As a result, a silicon single crystal layer is formed on the substrate W, which is the workpiece. This process continues until the film formation is completed after a predetermined time has elapsed. When the film formation is completed, the process proceeds to S109, where the susceptor 9 and preheat ring 32 are moved to the workpiece removal position, and in S110, the workpiece after film formation (i.e., the silicon epitaxial wafer EW in FIG. 2) is removed.

Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, in the above embodiment, a single-wafer apparatus that manufactures silicon epitaxial wafers by CVD (Chemical Vapor Deposition) is exemplified as the vapor phase growth apparatus 1, but the object to be manufactured is not limited to silicon epitaxial wafers. For example, the present invention can be applied to an apparatus that epitaxially grows a compound semiconductor single crystal layer on a single crystal substrate such as sapphire or silicon by MOVPE (Metal-Oxide Vapor Phase Epitaxy).

In addition, the height direction holding position of the susceptor 9 in the silicon single crystal thin film growth process (and thus the height direction dimension of the raw material gas flow space 5A) can be configured to be able to be selected and set to any of three or more predetermined values, or it can be set to be able to hold any position steplessly within a predetermined numerical range. In this case, the lifting and lowering drive parts of the susceptor position changing mechanism 39 and the preheat ring position changing mechanism 12 can be configured with a well-known screw shaft mechanism driven by a servo motor instead of the air cylinders 41 and 42. Figure 11 shows an example of a screw shaft mechanism, in which the rotation output of a motor 91 is transmitted to a screw shaft 95 via gears 93 and 94. The screw shaft 95 is screwed into a nut part 96 that penetrates the substrate BP (a concept that collectively refers to the substrates BP1 and BP2 in Figure 1), and is rotated and driven by the motor 91 to raise and lower the substrate BP supporting the susceptor 9 or the preheat ring 32 so that it can be held at any height position. Reference numeral 91s denotes a limit switch (origin detection unit) for detecting the origin position in the height direction of the substrate BP.

In this case, in the control system of FIG. 8, the set of air cylinders 41, 42 and cylinder drivers 41c, 42c is replaced with the corresponding screw shaft drive units 81 (for raising and lowering the susceptor) and 82 (for raising and lowering the preheat ring), shown by dashed lines. The electrical structures of these are substantially the same, and will be described as representative. That is, the motor 91 that drives the screw shaft 95 (FIG. 11) is connected to the input/output unit 74 via the servo control unit 91c. The servo control unit 91c drives the motor 91 to rotate in the downward direction upon initialization. Then, when the substrate BP activates the limit switch 91s, the motor 91 stops rotating and resets the counter for counting the pulse input from the pulse generator 91p (angle sensor) attached to the output shaft of the motor 91. Next, the target pulse number is set according to the set values of the susceptor height and preheat ring height from the control computer 70, and the motor 91 is driven in the upward direction. Then, when the number of pulses counted by the counter reaches the target pulse number, the motor 91 stops rotating. In this case, the set value table 72b in FIG. 9 is configured to include the values of the preheat ring height direction position P1', P2', P3, ..., the temperatures T1, T2, T3, ..., the flow rates F11, F12, F13, ..., and F21, F22, F23, ..., which correspond to three or more values P1, P2, P3, ... of the susceptor height direction position.

Although the embodiment of the present invention has been described above, the present invention is not limited to these. Below, a modified example of the lifting and lowering sliding part of the preheat ring 32 illustrated in FIG. 3 will be described with reference to FIG. 12 (common components to those in FIG. 3 are given the same reference numerals and detailed description will be omitted). In FIG. 12, the liner base 31 in FIG. 3 is replaced with a liner base 131. The liner base 131 is formed in a ring shape and has a sliding counterbore portion 131F formed along the upper inner peripheral edge. In addition, the liner movable portion 33 in FIG. 3 is replaced with a liner movable portion 133. The lower end side of the liner movable portion 133 is inserted into the sliding counterbore portion 131F of the liner base 131, and the outer peripheral surface slides up and down while being guided along the inner peripheral surface of the sliding counterbore portion 131F. The inner peripheral surface of the sliding counterbore portion 131F and the outer peripheral surface of the liner movable portion 133 are both cylindrical surfaces.

The preheat ring 32 is fitted into the first countersunk portion 133K so that its upper surface coincides with the upper surface of the liner movable portion 133. In addition, the tip of the connection auxiliary portion 35 is connected to the connecting frame 134 that is fitted into the second countersunk portion 133L of the liner movable portion 133.

In the above structure, the outer peripheral surface of the liner movable part 133 to which the preheat ring 32 is directly attached slides vertically inside the liner base 131 while being guided by the inner peripheral surface of the liner base 131, so that the effect of easily maintaining the horizontality of the preheat ring 32 when changing the height-direction holding position of the preheat ring 32 is achieved in the same way as in the case of adopting the structure of FIG. 3. In addition, the sliding surface on the liner base 131 side against the liner movable part 133 is changed from the two inner peripheral surfaces of the groove portion 31g in FIG. 3 to the single inner peripheral surface of the sliding countersunk portion 133F, so that the cross-sectional shapes of both the liner movable part 133 and the liner base 131 are significantly simplified compared to the configuration of FIG. 3, which has the advantage of making them easier to process.

1 Vapor phase growth apparatus 2 Reaction vessel body 3 Lower body 4 Upper body 4C Ceiling plate 5 Internal space 5A Raw material gas flow space 5B Equipment arrangement space 7 Exhaust pipe 9 Susceptor 9A Sleeve 9B Counterbore 11 Infrared heating lamp 12 Preheat ring position change mechanism 12A Lift pin drive arm 12B Lifting sleeve 12C Lift plate 13 Lift pin 14 Insertion hole 15 Rotating shaft member 15A Shaft body 15B Temperature sensor 15D Susceptor support arm 15C Coupling pin 21 Gas inlet 22 Gas exhaust port 29 Lower liner 30 Upper liner 31, 131 Liner base 32 Preheat ring 33, 133 Liner movable part 33A Sliding part 33B Flange part 31g Groove part 35 Coupling auxiliary part 39 Susceptor position change mechanism 40 Motor 41, 42 Air cylinder 133F Sliding counterbore EL Silicon single crystal thin film EW Silicon epitaxial wafer G Source gas h First dimension h' Second dimension O Rotation axis PP Main surface W Silicon single crystal substrate

Claims (10)

A vapor phase growth apparatus for vapor-growing a semiconductor single crystal thin film on a main surface of a single crystal substrate, comprising:
the reaction vessel body has a gas inlet formed at a first end side in a horizontal direction and a gas outlet formed at a second end side, the single crystal substrate is rotated and supported substantially horizontally on a disk-shaped susceptor which is rotated in an internal space of the reaction vessel body, a source gas for forming a semiconductor single crystal thin film is introduced into the reaction vessel body from the gas inlet and flows along the main surface of the single crystal substrate and is then discharged from the gas outlet, and a preheat ring is disposed so as to surround the susceptor,
a susceptor position changing mechanism that changes a height direction holding position of the susceptor within the reaction vessel body based on raising and lowering of the susceptor in order to change stepwise or steplessly a height direction dimension of a source gas flow space formed between the main surface of the single crystal substrate mounted on the susceptor and a lower surface of a ceiling plate of the reaction vessel body;
a preheat ring position changing mechanism that changes a holding position of the preheat ring in the height direction within the reaction vessel body based on raising and lowering of the preheat ring in a manner that follows a change in the holding position of the susceptor in the height direction;
A vapor phase growth apparatus comprising: The vapor phase growth apparatus according to claim 1, wherein the preheat ring position change mechanism changes the height-wise holding position of the preheat ring so that the main surface of the single crystal substrate on the susceptor coincides with the upper surface of the preheat ring when the height-wise holding position of the susceptor is changed. the susceptor position changing mechanism changes a holding position of the susceptor in a height direction between a susceptor-side first position, in which a height direction dimension of the raw material gas flow space is a first dimension, and a susceptor-side second position, in which a height direction dimension of the raw material gas flow space is a second dimension smaller than the first dimension,
3. The vapor phase growth apparatus according to claim 1, wherein the preheat ring position change mechanism changes a height direction holding position of the preheat ring between a ring side first position and a ring side second position corresponding to the susceptor side first position and the susceptor side second position, respectively. the susceptor is rotated via a rotating shaft member whose upper end is coupled to a lower surface of the susceptor, and the susceptor position changing mechanism raises and lowers the susceptor together with the rotating shaft member,
4. The vapor phase growth apparatus according to claim 1, wherein the preheat ring position changing mechanism comprises: a lift sleeve arranged coaxially outside the rotating shaft member and capable of being raised and lowered along the axis of the rotating shaft member while allowing the rotating shaft member to be rotated; a connecting member connecting the lift sleeve and the preheat ring; and a lift drive unit driving the lift sleeve and the connecting member to be raised and lowered together. a lift pin for lifting up the single crystal substrate on the susceptor from below, the lift pin having a lower end protruding downward from the susceptor;
5. The vapor phase growth apparatus according to claim 4, wherein a base end side of a lift pin drive arm for urging said lift pins upward from below is connected to said lift sleeve. a ring-shaped lower liner disposed around the susceptor in the reaction vessel body at a position where its outer circumferential surface faces the gas inlet; and a ring-shaped upper liner disposed above the lower liner in an opposing manner, for guiding a flow of the source gas, which is supplied from the gas inlet and which hits the outer circumferential surface of the lower liner and disperses in a circumferential direction while overcoming the lower liner, onto the main surface of the single crystal substrate on the susceptor;
the lower liner includes a liner base that forms the outer peripheral surface and is attached to the reaction vessel body in a fixed vertical position, and a liner movable part that has the preheating ring attached to an upper surface thereof and is attached to the liner base so as to be slidable in the vertical direction together with the preheating ring,
6. The vapor phase growth apparatus according to claim 4, wherein the connecting member is made up of the liner movable part and a connecting auxiliary part having one end connected to the lift sleeve and the other end connected to the liner movable part. the preheat ring is attached to the movable liner portion so that an upper surface of the preheat ring coincides with an upper surface of the movable liner portion;
7. The vapor phase growth apparatus of claim 6, wherein the preheat ring position changing mechanism changes the heightwise holding position of the preheat ring so that the main surface of the single crystal substrate on the susceptor coincides with the upper surface of the preheat ring as the heightwise holding position of the susceptor is changed. The vapor phase growth apparatus according to claim 7, wherein the movable liner part has a cylindrical sliding part whose base end is inserted into a groove that opens on the upper surface of the liner base and is engraved along the circumferential direction of the liner base, and which slides up and down within the groove, and a flange part that extends radially inward from the upper end edge of the sliding part, and the preheat ring is attached to the upper surface of the flange part. The vapor phase growth apparatus according to claim 7, wherein the liner base is formed in a ring shape and has a sliding counterbore along the upper inner periphery, the liner movable part is formed in a ring shape and the base end side is inserted into the sliding counterbore of the liner base, and the outer periphery slides up and down while being guided along the inner periphery of the sliding counterbore. The reactor vessel body has a gas inlet formed on a first end side in the horizontal direction and a gas outlet formed on a second end side, and a single crystal substrate is rotated and supported approximately horizontally on a disk-shaped susceptor that is rotated in the internal space of the reactor vessel body. A raw material gas for forming a semiconductor single crystal thin film introduced into the reactor vessel body from the gas inlet flows along the main surface of the single crystal substrate and is then discharged from the gas outlet. A preheating ring is disposed to surround the susceptor. Furthermore, the height dimension of the raw material gas flow space formed between the main surface of the single crystal substrate mounted on the susceptor and the underside of the ceiling plate of the reactor vessel body is stepped. A method for manufacturing an epitaxial wafer, comprising: a susceptor position change mechanism that changes the height direction holding position of the susceptor in the reaction vessel body based on the elevation of the susceptor in order to change the height direction holding position stepwise or steplessly; and a preheat ring position change mechanism that changes the height direction holding position of the preheat ring in the reaction vessel body based on the elevation of the preheat ring in a manner that follows the change in the height direction holding position of the susceptor; placing the single crystal substrate in the reaction vessel body; and circulating the source gas in the reaction vessel body to epitaxially grow the semiconductor single crystal thin film on the single crystal substrate in a vapor phase to obtain an epitaxial wafer.

Images